For the air conditioning of motor vehicles, use is made of non-combustible refrigerants in order to avoid the risk of an explosion in the vehicle interior compartment in the event of a collision. The refrigerants that have hitherto been used have however either already been banned, or are at least regarded as problematic, owing to their high global warming potential. One possible environmentally compatible, non-combustible refrigerant is CO2 (R744), which has already partially replaced the previous refrigerants. CO2 air conditioning systems however operate with high operating pressures, which place particular demands on the strength and sealing action of the system components. The advantage associated with the high operating pressure consists in that, owing to the relatively high density of CO2, a lower volume flow rate is required to impart a relatively high level of refrigeration power.
A scroll-type compressor for a CO2 vehicle air conditioning system is disclosed in JP 2006/144635 A. In general, scroll-type compressors of said type have rotational-speed-regulated electric drives in order to control the refrigeration power of the compressor. In conjunction with vehicle air conditioning systems that operate with conventional, low-pressure refrigerants, scroll-type compressors of simple construction are also known in which power regulation is realized by virtue of the compressor being activated or deactivated.
Accordingly, U.S. Pat. No. 6,273,692 B1 discloses a scroll-type compressor having a mechanical drive which can be connected to the compressor unit by means of an electromagnetic clutch. US 2002/0081224 A1 discloses a variable low-pressure scroll-type compressor which can be deactivated and activated by means of a radial movement of one of the two scroll spirals. Here, the eccentricity between the two scroll spirals is eliminated, which scroll spirals accordingly pass out of engagement in the radial direction.
In the known scroll-type compressors, the sealing action between the compressor spiral and counterpart spiral is a problem that has an effect on performance.